1. Field of the Invention
The present invention relates to a pusher device which feeds plate-form articles such as lead frames to a working device such as bonding machines.
2. Prior Art
One example of a conventional device that conveys plate-form articles such as lead frames, etc. is shown in FIG. 6.
As shown in FIG. 6, a main conveyor 2 is installed in front of a multiple number of working devices 1A, 1B, . . . These devices perform the same work such as wire bonding, for example. The lead frames 3 conveyed by the main conveyor 2 are supplied to the respective working devices 1A, 1B, . . . in the following manner:
The lead frames 3 are transferred to first subconveyors 4 from the main conveyor 2 and then to points which are above the guide rails 5. Then, the first sub-conveyors 4 are lowered so that the lead frames thereon are placed on the guide rails 5. Afterward, the lead frames 3 are fed out to conveyors 7 by pushing members 6 of a pusher device. The lead frames 3 are fed at fixed intervals by the conveyors 7 and worked by the working devices 1A, 1B, . . . After the working is completed, the lead frames 3 are fed out onto guide rails 8 and then conveyed by second sub-conveyors 9 to the main conveyor 2. The lead frames 3 are thereafter transferred to the next process or stored in a storage magazine by the main conveyor 2.
Japanese Patent Application Laid-Open (Kokai) Nos. 62-235122, and 3-158317 and Japanese Patent Application Publication (Kokoku) N. 1-31688 are examples disclosing the conveyor devices of this type.
In the conveyor devices as described above, the lead frames 3 are conveyed onto the guide rails 5 by the first sub-conveyors 4 and then pushed onto the conveyors 7 by the pushing members 6 so that a predetermined working is performed on the lead frames 3. Accordingly, the pushing members 6 are installed so that they are positioned at the rear ends of the lead frames 3 that have been transferred onto the guide rails 5. As a result, when the lead frames of different types that are different in length are to be fed to the working devices, the positions of the pushing members 6 need to be adjusted so as to comply such a different length by moving the pusher device back and forth and otherwise.
As described above, since the pushing members 6 are positioned so as to be at the rear ends of the lead frames 3 on the guide rails 5, if the positions of the pushing members 6 are moved due to the changes in the length of the lead frames, the pushing members 6 may strike against the first sub-conveyors 4. In order to avoid the striking, the pusher may be designed to be vertically movable.
In this type of pusher, when the lead frame guides of the first sub-conveyors 4 are positioned above the guide rails 5, the pusher device is raised so that the pushers 6 can be positioned above the sub-conveyors 4. Then, the sub-conveyors 4 are lowered so that the lead frames 3 thereon are transferred onto the guide rails 5; thereafter, the pusher device is lowered so that the pushing members 6 are positioned at the rear ends of the lead frames 3.
Thus, since a vertical driving means is required to raise and lower the pusher device, the cost of the apparatus tends to be high. In addition, since the pushing members 6 must be actuated after the pusher device has been lowered, the supply of the lead frames 3 to the working devices 1A, 1B, . . . is not accomplished immediately.